It's not pH that's important, it's GH (hardness). If you are on mains water, your water provider's website should tell you your hardness.
The way to tell if that cute fish is right for your tank is to know your hardness before you go shopping, then use your phone to look the cute up fish on Seriously Fish
www.seriouslyfish.com
The fish profiles on there tell you the hardness (GH), pH, temperature, tank size, etc that the fish needs. They tell you if there are any quirks like the fish being aggressive, or if they need to be in a group, or if they need a particular kind of food.